Process for imparting durable loft and warmth to cellulosic fabrics



United States Patent 3 197 7 success non ruranhnsh Lori" ANB WARP relTil FABRKCS Nelson l. Gete ll Gr at Falls, Va, assignor to (lotionProducers institute of The National Cotton Council of America, Memphis,Tenn, a corporation of Tennessee No Drawing. Qontinuation of applicationSer. No.

13%,330, Mar. 16, E62, application May 6,

Ser. No. 365,436

4 Claims. (Cl. EZ1?.6)

This application is a continuation of my application Serial No. 180,330,filed March 16, 1962, now abandoned.

The present invention relates to a process for imparting desirablecharacteristics to cellulosic materials and, more particularly, to aprocess for treating lofty cellulosic materials whereby the loft of thecellulosic material is retained even after repeated launderings andextended periods of use.

It is well known that the insulating value of a fabric, and thereforeits warmth, depends upon the immobilized or dead air entrapped in theinterstices between the fibers and between the yarns, rather than uponthe insulating characteristics of the individual fibers of the fabric.Hence, the warmth of a fabric may be described as being a function ofits thickness, or loft, and the insulating properties of the fabric areexcellent when the ratio of the volume of entrapped air to the fibers ofthe fabric is large.

While it has been possible to produce lofty cellulosic materials, suchas cellulosic fabrics, suitable for use in winter weight clothing,blankets, and the like, and these articles have initially had goodwarmth characteristics and a good appearance, they have had theprincipal disadvantage that after a period of use and/or after repeatedlaunderings, the lofty characteristic of the material is substantiallydecreased, due to the matting of the fibers. Once the cellulosic fibersof the fabric become compressed, the fabric cannot recover its previouslofty condition due to the poor resiliency of the fibers. The cellulosicfabric not only loses its original lofty appearance but also loses itssoftness and a substantial portion of its insulating or warmthproperties. Even though cotton fibers, per se, are durable in that theycan undergo unlimited and repeated launderings and can withstand harshtreatment, cellulosic materials, such as cotton fabrics, are not aswidely used as they could be in the making of winter weight garments,such as sweaters, suits, jackets, and the like, because of the aforesaiddisadvantages resultin from the inability of the material to retain itslofty appearance.

While cotton is abundant in this country and is less expensive thanother fibers, both natural and synthetic, it has been unable to competecommercially with these other fibers in those areas where a durable loftis a principal prerequisite of the finished article.

The field of winter weight fabrics represents a very large potentialmarket to the cotton industry. This market has been dominated by woolfor many years, but during the last several years the manufacturers ofsynthetic fibers and fabrics have been making spectacular gains throughthe use of their bulk or textured yarns. Fabrics made from this new typeof synthetic yarns or blends of wool and synthetic fibers have becomeincreasingly popular for such uses as mens, womens, and childrenssweaters, coats, suits, and other outerwear garments. The successfuldevelopment of cotton fabrics having the desired esthetic and physicalproperties would significantly improve cottons competitive position inthe field of winter weight fabrics.

Accordingly, it is an object of this invention to obviate the abovedisadvantages which are present with respect to maintaining a durableloft on cellulosic materials.

ice

Another object of this invention is to provide a process for treatingcellulosic materials whereby the loft of the material is retained evenafter the material has been subjected to repeated laundering operations.

It is another object of this invention to provide lofty cellulosicmaterials, including cotton textile fabrics, which are well-suited foruse in making warm, insulating winter weight garments, blankets, and thelike, and which have the ability to retain their loft and appearance,and thus their insulating characteristics, even after being launderedrepeatedly.

in attaining the objects of this invention, one feature resides insubjecting the cellulosic material to a bath containing a crosslinkingagent capable of reacting with the cellulosic fibers of the material,extracting the excess of the agent, drying the material and, prior toreacting the agent with the cellulosic material, subjecting the drycellulosic material to a mechanical action, such as tumbling, brushing,iluffing, or the like, whereby the material is lofted and maintained inthis lofty condition while the material is subjected to the conditionsnecessary to cause the reaction between the cross-linking agent and thecellulose to be completed.

Another feature resides in mechanically agitating the treated cellulosicmaterial while simultaneously drying the material in order to restorethe lofty condition to the material, and then subjecting the treatedmaterial to the conditions necessary to effect a cross-linking betweenthe reagent and the cellulosic fibers.

A further feature resides in imparting a loft to a cellulosic materialand, while maintaining the lofty condition of the material, applyingthereto an amount of a cross-linking reagent at least suiiicient to setthe fibers in their lofty condition, and reacting the reagent with thecellulosic material to set the fibers.

Other objects, features, and advantages will be apparent from thefollowing description of the invention.

It has been discovered that the objects set forth above, as well asothers, can be obtained by first treating the cellulosic textilematerials with any of the many different reagents presently used toenhance the crease resistance of cellulosic textiles and/ or to givewash-and-wear characteristics thereto, and, prior to reacting thereagent on the material, bringing the cellulosic material to its loftycondition and setting the material in this condition during the curingstage of the reagent. The cellulosic material, which may be a cottontextile, including a woven or non-woven fabric, or the lik then retainsits loft through repeated launderings and fabric deformations.

More specifically, lofty cotton textile fabrics are first treated witheither a solution, suspension, dispersion, or a paste of an organiccross-linking reagent which is applied to the fabrics by anyconventional method such as dipping, spraying, brushing, immersion,padding, coating, or the like. The excess reagent is then removed fromthe cellulosic material by any known means, such as by squeezing betweenrollers, by passing over vacuum slots, or by centrifuging, and the like.The fabric which now has its fibers in a compressed or matted condition,is mechanically worked until its lofty condition is restored; i.e.,there is an increase in the thickness of the fabric and an increase inthe ratio of the volume of entrapped air to the volume of the cottonfibers. This mechanical working is carried out by either tumbling,brushing, or flufiing the fabric, or by other procedures whichaccomplish the same effect, while the fabric is being simultaneouslydried at a relatively low temperature to remove unwanted moisture.Alternatively, the drying may be carried out before the treated fabricis subjected to the aforesaid lofting step.

Following thes subjected to the e operations, the treated lofty fabricis particular conditions necessary to cure the reagent. This may beaccomplished by the use of high temperatures, or by the presence ofalkaline or acidic conditions, or by the action of other factors,depending upon the reagent used, thereby setting the fabric in its loftyconfiguration. As a result of this process of lofting by the presentinvention, the fabric returns to its lofty configuration after repeatedwashings and deformations. Fabrics not subjected to the lettingoperating become matted and compressed and their surfaces may becomedisarrayed and less attractive after repeated launderings.

For purposes of this invention, the reagents which are used in treatingthe lofty cellulosic material and which are cured thereon to set thematerials in their lofty condition are identical to those which havebeen used by the cotton industry for imparting crease-proofing and/ orwash and wear characteristics to cellulosic materials. These reagentswill be referred to as cross-linking reagents in this specification andclaims, even though the art is not certain that these reagents actuallycross-link the cellulosic molecules of the fibers. stricted to anytheory as to why the results are achieved, since the fact remains thatthey are achieved. Thus, the term cross-linking reagents is to beunderstood to include the group of chemicals which are known orrecognized by the art to impart crease-proofing and wash and wearproperties to cellulosic fabrics.

Among the various and well known cross-linking reagents which may beused in the process of this invention are the aldehydes, such asformaldehyde; polyacetals, which are the products of a reaction betweenaldehydes and polyalcohols; methylol urea precondensates, such asdimethylol urea; cyclic methylol urea compounds, such as dimethylolethylene urea, i.e. 1,3-bis-(hydroxymethyl)-2- imidazolidone; triazonessuch as 1,3-dimethylol-5-hydroxy ethylperhydrotriazone-2; methylolmelamine compounds and triazines, such as are produced by reactingmelamine with formaldehyde; epoxides and related compounds, such asdiglycidyl ether of ethylene glycol; and tris-l-aziridinyl phosphineoxide which imparts both crease and flame resistance to the cellulose;dichloropropanol; and ethyl carbamate.

Also included as cross-linking agents within the meaning of this termfor the present invention, are condensatlon products of formaldehydewith acetone, with acrolein, with acetone and acrolein, with phenol,with diethylene glycol dicarbamate, with formamide, with hydroxylamines, with polymerized methacryl amides, with urea and alkylene oxidesand epichlorohydrin, with tetrahydroimmopyrimidine, with hydrazines ofmonoand dicarboxylic acids, with low-molecular weight polyesters orpolyurethane, with nitrilotripropionam-ide, with glyoxal and urea, withhexamethylene diamine and urea, with hexose ureides, with dicyandiamideand urea, and with 2-oxo-4,5-diimino parabanic acid resins; the urons;chloromethyl ethers of polyhydric alcohols; dicarboxylic acid anhydridesand diesters; copolymers of ethylenic di-carboxylic acids with vinylcompounds; salts of poly (vinyloxyalkyl) amines; cyclopropyl quaternaryammonium compounds; silicones and resin precondensates; quaternaryammonium derivatives of silicones, and halo-silanes; bis-(hydroxymethylurethane) of 1,4-butanediol; orthophosphoric acid, urea,and sodium hydroxide; diisocyanates; aldehyde-ethylene imine reactionproducts and phosgeneethylene imine reaction products; formyl alkyloxetanes; divinyl sulfone, its derivatives, and vinyl sulfone-ureaaddition products; onium compounds; and rubber latex with chloromethylethers. Mixtures of any of the above may also be used.

While all of the above cross-linking reagents are known to produce thedesired results on cellulosic fabrics, among the ones which are usedcommercially by the cotton industry to impart the desired creaseproofingor wash and wear properties are included cyclic ethylene urea, 1,3-dimethylol-S-hydroXyethyl-perhydrotriazone-2, diglycidyl ether ofethylene glycol, tris-l-aziridinyl phosphine oxide Applicant does notwant to be re- 4 and divinyl sulfone or divinyl sulfone donors, i.e.,compounds which. form divinyl sulfone during the treatment of thefabric. Also included are the melamine formaldehyde precondensates.

Some of the above-listed cross-linking reagents require the presence ofcatalysts during the curing step, while others, such as trimethylolphenol, do not. The f0rmaldehyde resins usually require acidiccatalysts, while others, such as divinyl sulfone, require alkalinecatalysts. Hence, whether a catalyst is used and whether it is acidic orbasic will depend upon the particular cross-linking reagent used.Generallthe catalysts belong to the following groups: organic acids,such as maleic, acetic, tartaric, oxalic, lactic, etc.; inorganic acids,such as hydrochloric; metal salts, such as aluminum, magnesium, copper,zinc, and calcium ch10;

rides, zinc nitrate, zinc fiuoroborate and the like; ammonium salts,such as ammonium chloride, ammonium phosphate, ammonium sulfate, etc;organic amine salts such as the hydrochloride salts; alkali hydroxidesand carbonates; as well as many others which will readily come to mind,depending upon the particular cross-linking reagent to be used.

In the same manner, the temperature of the curing step, the length oftime for the cure, etc., will depend on the reagent-catalyst systememployed, and the weight and type of fabric being treated. These arematters which are well known to those skilled in the art.

The amount of cross-linking reagent which is deposited on the cellulosictextile will usually vary from about 1 to about 15% by weight of thecellulosic textile. Amounts larger than 15% by weight may be used, ifdesired, but generally there is no additional advantage to be gainedthereby. In fact, some beneficial results are obtained even when theamount of cured reagent on the fabric is less than 1% by weight of thefabric.

The solution, dispersion, or emulsion preferably used for immersion ofthe cellulosic material is an aqueous one as a matter of convenience andavailability, since most commercial cellulose textile processors preferto use aqueous systems rather than the more costly non-aqueous systems.Any suitable solvent may be used, however, depending upon which systemis to be utilized. Wetting agents may also be present in the treatingbath along with softeners, lubricants, stiffening agents, and the handmodifiers, as well as other conventional finishing agents.

In the following examples, which are only illustrative of the inventionand are not to be considered as limiting the invention in any way,various cellulosic textiles were subjected to the process of theinvention, and the appearance of the pile and the feel of the treatedtextiles were evaluated. The thickness and compressibility were measuredwith a compressometer as described by H. F. Scheifer, J. Res. Nat,Bureau of Standards 10, 705 (1933), RB. 561; and the compressibility wasevaluated as follows:

z p essibility, p r llti where t is the thickness at the pressuresindicated.

Example I A treating solution was prepared which contained 24.5%dimethylol ethyl triazone having the formula nornonriiawomon and 2.9%maleic acid as a catalyst therefor, the remaindor being water. Samplesof a commercial cotton blanket were immersed in this solution and paddedto wet pickups of approximately of fabric weight. The samples were thentumbled in a tumble dryer without heat for 15 minutes, then tentered,and lightly brushed. They were then dried at 220 F. until dry to thetouch, and then cured for 2 minutes at 320 F. The dry add-on aftercuring was approximately 12.5 The samples were given a light scour toremove residual reagents. Their thickness was superior to and theappearance of their pile similar to that of the original samples.

Example 11 Treatment of the sample was exactly like that described underExample 1 except that the brushing of the pile was omitted. Gn asubjective rating scale on which the appearance of the original pilerated and on which a very disturbed, unsightly pile rated 0, the pile ofthe treated sample was rated 8 after the scour. *lowever, after 10typical laundering cycles in an automatic home washing machine, theappearance of the treated sample was superior, being rated 5 while thatof the untreated sample was rated 1. The thickness of the treated sampleafter the process wash was 116 mils, and its compressibility 41%; thecorresponding figures for the original sample were 80 mils, and 31%;these results indicate the better loftiness of the treated sample.

Example 111 The treatment of the sample was like that described underExample ll except that the concentration of the triazone was 13.4%, andthat of the maleic acid catalyst was 1.6%. This resulted in a slightlylower thickness and poorer retention of the pile appearance. Thus, thethickness after scouring was 109 mils, the compressibility 44%, and therating of the pile appearance after 10 launderings was 3.

Example IV This treatment was like that described under Example IVexcept that the dimethylolethylene urea concentration was 11%, and thezinc nitrate concentration 1%. This resulted in improvement of thethickness and compressibility similar to that in Example IV but inbetter retention of the pile appearance in laundrering. Thus, thethickness after the scouring was 121 mils, the compressibility 40%, andthe rating of the pile appearance after 10 launderings was 6.

Example Vl This treatment was like that described under Example V exceptthat 1% (based on fabric weight) of a polyeth lene softener was added tothe bath. This resulted in a softer hand but somewhat lower thickness ofthe sample, and poorer retention of the appearance of the pile. Thus,the thickness after scouring was 98 mils, the compressibility 44%, andthe pile appearance rating after 10 launderings was 5 Example VII Thistreatment was like that described under Example V except that the samplewas padded through a 1% (based on fabric weight) solution ofpolyethylene softener after curing, and dried at 220 F. This resulted ina softness of the sample similar to that obtained in Example VI, in athickness between that obtained in Examples V and VI, and in somewhatbetter retention of the pile appearance in repeated laundering than inExamples V and VI. Thus,

after scouring the thickness was 113 mils, the compressibility 41%, andthe pile appearance rating after 10 launderings was 7.

6 Example- VIII The treatment was like that described under Example Vexcept that 2% polyvinyl acetate was added to the bath. This resulted ina somewhat harsher, scoopier hand or feel than that in Example V, butrelatively little change in loft and pile appearance. The thickness ofthe sample after scouring was 113 mils, the compressibility 39%, and thepile appearance rating after 10 launderings was 5.

The presence of a harsher, scroopier hand or feel in the cotton textile,such as achieved by the process of Example VIII, may be desirable inmany instances, particularly with respect to cotton blankets and certainwinter wear garments. Modified urea-formaldehyde polymers, or otherknown hand stiffeners, may be used in place of the polyvinyl acetate ofExample VIII, for achieving substantially the same results.

The principle of the present invention is applicable to cellulosicmaterials including fibers, filaments, yarns, textile fabrics includingwoven and non-woven textiles and fabrics, and the like, as well asmaterials formed from blends of cellulosic fibers with other fibers,whether natural or synthetic, which cellulosic materials either have alofty configuration or can be so treated as to impart thereto a loftyconfiguration. When treated with the process of this invention, suchcellulosic materials retain this lofty configuration even after repeatedlaunderings or deformations. Included in the term cellulosic are cotton,rayon, and linen materials, and this term is not to be restrictive inany manner. Ramie, hemp, jute, and the like are other examples ofcellulosic materials.

While the invention is primarily concerned with'the retention of theloft of the cellulosic material, the principles of the invention arealso applicable to those cotton fabrics which as manufactured have noloft originally but which have the capacity to be lofted, if desired,such as some loosely woven materials coming directly from a loom. Suchmaterials can be lofted by mechanical action as described in thisapplication and then treated with the cross-linking reagents inaccordance with the invention, so as to retain the loft.

Furthermore, cellulosic materials including napped fabrics, pilefabrics, tweed, and other winter weight cellulosic materials which arein a lofty condition can be treated so as to retain the lofty appearanceeven after launderings, deformations, and the like, by subjecting thematerials while in their lofty condition to a fine mist or a vapor ofthe cross-linking reagent for a period of time sufficient to deposit thenecessary amount of the reagent on the material and then curring thedeposited reagent, care being taken to maintain the loft of the materialduring the deposition and curing phases.

Other modifications will be apparent to those skilled in the art withoutdeparting from the scope and spirit of this invention. Therefore, theclaims which appear below should be construed as encompassing all thefeatures of patentable novelty which reside in the present inventionincluding all features which would be treated as equivalents thereof bythose skilled in the art to which the invention pertains.

Iclaim:

E. A process for imparting to a cellulosic fabric the desirablecharacteristic of maintaining its appearance even after repeatedlaunderings and for increasing its thickness, compressibility, andinsulating properties, comprising applying to said cellulosic fabric acrosslinking reagent capable of reacting with the cellulosic moleculesor" said fabric and forming crosslinkages with said molecules, loftingthe fabric by mechanical agitation to increase the thickness of thefabric and increase the ratio of the volume of entrapped air to thevolume of cellulosic fibers and then curing the crosslinking reagent onsaid lofted fabric while said fabric has an increased thickness and hasthe volume of entrapped air to the volume of cellulosic fibersincreased.

2. The process as defined in claim 1 wherein said cellulosic fabric is awinter Weight fabric.

3. A process for imparting to a mapped, Woven cellulosic fabric thedesirable characteristic of maintaining its napped appearance even afterrepeated launderings and for increasing its thickness, compressibilityand insulating properties, comprising applying to said cellulosic fabrica crosslinking reagent capable of reacting with the cellulosic moleculesof said fabric and forming crosslinkages with said molecules, loftingthe fabric by mechanical agitation to increase the thickness of thefabric and increase the ratio of the volume of entrapped air to thevolume of cellulosic fibers and then curing the crosslinking reagent onsaid lofted fabric While said material has an increased thickness andhas the volume of en trapped air to the volume of cellulosic fibersincreased.

4. A process for imparting to a mapped, woven cellulosic blanket thedesirable characteristic of maintaining its napped appearance even afterrepeated launderings and for increasing its thickness andcompressibility and insulating properties comprising applying to saidcellulosic blanket a crosslinking reagent capable of reacting with thecellulosic molecules of said blanket and forming 8 crosslinkages withsaid molecules, lofting the fabric by mechanical agitation to increasethe thickness of the blanket and increase the ratio of the volume ofentrapped air to the volume of cellulosic fibers and then curing thecrosslinking reagent on said lofted blanket while said blanket has anincreased thickness and has the volume of entrapped air to the volume ofcellulosic fibers increased.

References Cited by the Examiner UNITED STATES PATENTS 2,080,043 5/37Heckert 8l 16.3 2,517,529 8/50 Stanley. 2,590,713 3/52 Libbey. 2,950,5538/60 Hurwitz 8-1163 X FOREIGN PATENTS 265,027 12/54 Australia.

497,647 12/38 Great Britain.

518,167 2/40 Great Britain.

547,846 9/ 42 Great Britain.

NORMAN G. TORCHIN, Primary Examiner.

1. A PROCESS FOR IMPARTING TO A CELLULOSIC FABRIC THE DESIRABLECHARACTERISTIC OF MAINTAINING ITS APPEARANCE EVEN AFTER REPEATEDLAUNDERINGS AND FOR INCREASING ITS THICKNESS, COMPRESSIBILITY, ANDINSULATING PROPERTIES, COMPRISING APPLYING TO SAID CELLULOSIC FABRIC ACROSSLINKING REAGENT CAPABLE OF REACTING WITH THE CELLULOSIC MOLECULESOF SAID FABRIC AND FORMING CROSSLINKAGES WITH SAID MOLECULES, LOFTINGTHE FABRIC BY MECHANICAL AGITATION TO INCREASE THE THICKNESS OF THEFABRIC AND INCREASE THE RATIO OF THE VOLUME OF ENTRAPPED AIR TO THEVOLUME OF CELLULOSIC FIBERS AND THEN CURING THE CROSSLINKING REAGENT ONSAID LOFTED FABRIC WHILE SAID FABRIC HAS AN INCREASED THICKNESS AND HASTHE VOLUME OF ENTRAPPED AIR TO THE VOLUME OF CELLULOSIC FIBERSINCREASED.